Optical lens generating machine having spherical bearing workpiece holder

ABSTRACT

An optical lens surfacing machine for separate operation upon each refractive side of an ophthalmic lens. The lens is carried by a pivotable workpiece holder. The holder permits total lens surface engagement by an operation tool, thereby providing a single machine for lapping and polishing a lens in a minimum number of steps.

United States Patent 1191 Blum et al.

1451 Aug. 13, 1974 OPTICAL LENS GENERATING MACHINE HAVING SPHERICAL BEARING WORKPIECE HOLDER [75] Inventors: Raymond T. Blum, Pittsford; George J. Laughman, Perinton, both of NY' [73] Assignee: Bausch & Lomb Incorporated,

Rochester, NY.

[58] Field of Search... 51/124 L, 126, 216 P, 217 L, 51/234, 277, 131, 284

3,488,174 1/1970 Boudet 51/284 X FOREIGN PATENTS OR APPLICATIONS 318,561 1/1920 Germany 5l/2l6 584,919 1/1947 Great Britain 51/124 L Primary ExaminerAl Lawrence Smith Assistant ExaminerNicholas P. Godici Attorney, Agent, or Firm-Frank C. Parker; Bernard D. Bogdon; Harry C. Post, 111

[5 7] ABSTRACT An optical lens surfacing machine for separate operation upon each refractive side of an ophthalmic lens. The lens is carried by a pivotable workpiece holder. The holder permits total lens surface engagement by an operation tool, thereby providing a single machine for lapping and polishing a lens in a minimum number [56] References Cited of Stem UNITED STATES PATENTS 1,639,012 8/1927 Tillyer et al 51 124 L 3 Claims 5 Drawing Figures 4? n 5 42 45 J I] R" I 1 52 PATENTYED mm 1 3.828.483

SHEET 1 BF 2 OPTICAL LENS GENERATING MACHINE HAVING SPHERICAL BEARING WORKPIECE HOLDER BACKGROUND OF THE INVENTION This invention pertains to an optical lens surfacing machine for operating upon a single surface of a lens and in particular, to an optical lens surfacing machine for performing individual lapping and polishing operations upon a single surface of a lens carried by a workpiece holder for automatically aligning the lens surface with an operation tool.

SUMMARY OF THE INVENTION An optical lens surfacing machine is provided to eliminate prism, defined as nonuniform lens thickness, from an ophthalmic meniscus lens and further, in separate operations to rough lap, fine lap and polish both sides of the lens to produce a finished ophthalmic lens of high quality. The simplicity of embodiments according to the principles of this invention enables a wide range of curvatures and sizes of high quality lenses to be finished at relatively inexpensive cost. In addition, disposing the work too] head above the workpiece greatly facilitates the introduction of slurry material during the processing steps and provides for automatic cleaning of the tool face for a current and subsequent operation.

It will be appreciated from this disclosure that any one machine, according to the discussed principles can be easily adjusted to accomplish rough lapping, fine lapping and polishing of either concave or convex sides of an ophthalmic lens. However, from a practical standpoint in a production situation, it is more readily desirable to set up individual machines to accomplish each task. With individual machines, a first machine initially rough generates one side of a pressed lens molded from a molten material. A second machine rough generates the opposite side and removes prism. Third and fourth machines, respectively,fine lap both sides and fifth and sixth machines each polish a respective side. Oscillation is provided during the polishing step to provide breakup to produce high quality finished lenses.

Machines according to the principles of this invention can be made quite sturdy and generally have a rotational tool supported about a yoke disposed over a centrally positioned pivotable chuck for carrying the lens material being operated upon. A pivotal axis of the yoke supporting the rotational tool can be easily adjusted to insure that the rotational axis passes through the center of curvature of the lens being formed regardless of whether it is concave or convex. In addition, a fine adjustment can be accomplished by easily raising or lowering the lens material carrying chuck to further accomplish having the axis of rotation of the tool and the optical axis intersect at the center of curvature of the lens surface defined by the spherical faced operation tool.

Even though it is desirable that the initial machine setup have the rotational axis of the operation tool intersect the vertical axis of the pivotal chuck and its support pedestal at the center of curvature of the lens surface being formed by the operation tool and for the pivotal axis of the yoke to intersect a plane defined by the rotational and before mentioned vertical axis at the center of curvature, these considerations are not particularly critical. Since the setup is not particularly critical as it is for a lens generation machine where most all operational members including the lens carrier are generally rigid and accurately positioned one to the other so as to insure that the lens being formed is manufactured to design this invention is a great advance over the prior art. With the inclusion of the pivotal chuck, as in the present invention, the critical accuracies necessary for setup of typical generation machines are not required for these improved machines. The pivotal chuck provides for total surface contact between the lens material and the operation tool without disturbing the optical axis of the meniscus lens which is first indentifiable after the first rough lap operation upon a pressed lens, as hereinbefore mentioned.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic illustration of a lateral view of a lens surface operation tool for operation upon, for example, a convex side of a lens material held in a ball chuck.

FIG. 2 is a schematic illustration of the front view of the lens surface operation tool and ball chuck of FIG. 1, showing the pivotal axis for operational oscillation upon the convex surface of lens material.

FIG. 3 is a cross-sectional view of a ball-bearing chuck for supporting lens material for operation upon a convex side of the lens material.

FIG. 4 is a cross-sectional view of a ball chuck for supporting lens material for operation upon a convex side of the lens material.

FIG. 5 is a cross-sectional view of a ball chuck for supporting lens material for operation upon a concave side of the lens material.

DESCRIPTION OF THE PREFERRED EMBODIMENT In FIGS. 1 and 2, respectively, are schematically illustrated lateral and front views of an embodiment constructed according to the principles of the present invention for operation upon lens material 10 to either rough lap, fine lap, or finish polish the lens material 19 into a high quality ophthalmic lens. As hereinbefore mentioned, it is most practical in a production situation to have individual machines accomplishing each of the respective lapping and polishing operations for each side of a lens being manufactured. Accordingly in FIG. 1, the illustration is for either lapping or polishing the convex surface of the lens material 10. The operation tool 12 is rotationally driven through a power driven connecting tool axis 14 to operate upon the total surface of the convex side of the lens material 10 when lowered in the downward direction of double headed arrow 16 to engage the lens material 10. It is preferred that the operation tool 12 cover at least two-thirds of the lens surface when engaged therewith. Under conditions of polishing, oscillation of the operation tool 12 about the center curvature identified by point X, is provided. It is generally not necessary to oscillate during lapping.

In the initial setup, a chuck 18 is caused to engage and carry the lens material 10 about the optical axis BB' to intersect the rotational axis A-A' at the center of curvature X of the lens material surfacing being operated upon. During a lapping operation, any of the exemplary chucks shown in FIGS. 3, 4 or 5 may be substituted for chuck 18. During the first two operations upon a lens material by an embodiment of the present invention, a pressing is placed in a ball-bearing chuck as illustrated in FIG. 3 to accomplish a rough lap of each respective side. A typical pressing, may be of hardened glass material having a meniscus shape formed in a mold from molten ophthalmic glass. It will be appreciated that the schematic illustration in FIG. I typically discloses an arrangement for rough lapping, fine lapping and polishing of either the convex side or the concave side of the lens material. Under any of those operations the appropriate lens operation tool 12 is incorporated for the specified operation and most usually a chuck like the chuck of FIG. 3 is included for generating or rough lapping and a chuck like the chuck of FIG. 4 or 5 is included for fine lapping and polishing with appropriate tool 12.

The configurations of the schematic illustrations in FIGS. 1 and 2 typically identifies an operational tool 12 disposed vertically above lens material engaged in the chuck 18 with a slurry introduction tube 19 present to introduce an appropriate slurry composition or fluid material during operation. This physical relationship, where the tool is above the workpiece, is maintained for all operational steps whether a step of generating, lapping, or polishing is being performed and regardless of whether a concave or convex surface of the lens material 10 is being operated upon. Although not illustrated, it is easily appreciated that slurry materials are flowed over the respective surfaces of the lens material 10 during the operational steps. It is well recognized that slurries of different composition are used in generating, lapping or polishing processing steps. Due to the hereinbefore described physical relationship of the operational tool 12 vertically disposed over the lens mate rial 10, particles of the lens material 10 that are being removed readily flow away from the work surface, particularly when a convex surface is being operated upon. Additionally, when a concave surface is being operated upon, the lens material 10 can be removed from the chuck 18 without being subjected to being drawn through a catch basin filling with removed material which is most likely to mar the lens material at its finished surface during the removal of the lens. A catch basin is formed if, for example, the operational tool is disposed directly below the lens material 10, as is true in some prior art devices. In addition, under conditions where a catch basin is formed by a work tool being disposed below the lens material, the basin needs to be cleaned before a next operation if a high quality operation is being performed. Otherwise, as is obvious, the undesirable previously removed materials are introduced between the lens material and work tool in the subsequent operation. a

The FIG. 2 illustration emphasizes the stability of the rotational operation tool 12 engaged in the yoke 20. The yoke 20 is pivotal about an axis CC which passes through the optical axis of the lens material 10 at the center of curvature X.'The yoke 20 pivots about the axis CC" while journaling in bearing supports 22 and 24, respectively, secured to center of curvature adjusting blocks 26 and 28 which are in turn affixed to a base 30. From FIG. 2, it is best seen that the base 30 provides the reference for operation and for affixing an adjustable length chuck pedestal 32 for carrying the chuck 18 which is free to pivot and rotate.

It will easily be appreciated from the description and illustrations that the center of curvature adjusting blocks 26 and 28 may be of any height size to raise or lower the axis C-C' relative to the'base 30 and the chuck pedestal 32 to establish flexibility for the machine in order to manufacture a singificantly wide range of curvatures for lenses whether they be for concave or convex surfaces. The center of curvature ad- 5 justing blocks 26 and 28 are for rough adjustment and fine adjustment is accomplished by moving the adjust able length chuck pedestal 32, as needed. in either of the directions identified by double headed arrow 33.

As hereinbefore mentioned, any of the three chucks, 34, 36 and 38 of FIGS. 3, 4 and 5, respectively may be used in accomplishing the lapping and polishing operations necessary to complete surface manufacture of an ophthalmic lens.

The chuck 34 of FIG. 3 is best used to lap and remove what is generally referred to as prism or sometimes defined as nonuniform thickness of the lens mate rial between the refractive surfaces. After a glass pressing 40 has had, for example, a concave surface generated upon it an according to the aforementioned principles of this invention, the next operational step is to rough lap the convex side of the lens material 40. This next step and subsequent surfacing steps are all by embodiments according to the principles of the present invention. As a first measure the lens material 40 is secured within a suitable seat in a rotatable chuck head 42 of the chuck 34. From FIG. 3 it will be appreciated that the chuck head 42 is rotatable about a ball bearing assembly 46 having a plurality of typically illustrated balls 45. A race 44 of the ball bearing assembly 46 is affixed to the chuck head 42 and an opposite mating race 48 is in turn affixed to a spherical bearing 50. In addition to the rotatability of the chuck head 42, the chuck head 42 is movable relative to the chuck pedestal 32 to provide automatic alignment of the lens material 40 when engaged with the operation tool 12. Toward this end, movement of the spherical bearing 50 relative to a bearing mount 52 in any 360 direction, as partially identified by double headed arrow 54 to designate movement in the plane of the illustration, may then be provided. Materials of the spherical bearing 50 and the bearing mount 52 are such that the spherical bearing 50 is able to move in, for example, either of the directions indicated by double headed arrow 54 without a great deal of force being exerted in any nonradical direction relative to the center of the spherical bearing mount 52. Due to a satisfactory level of static friction force between the spherical bearing 50 and the spherical bearing mount 52, a lapping tool at surface tool 12, when engaged with the lens material 10, will more fully encounter any high areas on, for example, the convex lens surface of a lens having an opposite generated concave lens surface. The contact encounter at the high areas of the lens material and the surface tool will be for fractional periods of time longer than would occur if the lens material 10 were mounted in a chuck similar to chuck 36 which is more free to move without noticeable effect due to any static friction force component. This slightly longer duration of tool and lens material encounter is all that is needed to remove high areas on the lens and to make the refractive surfaces uniformly distant from each other across the lens and thus remove prism. The level of static friction force between the spherical bearing 50 and the spherical bearing mount 52 which is necessary to accomplish these desirable results in a function of the bearing and mount materials and other factors including work tool surface material, workpiece material and rate of engagegnent of the tool and workpiece. In addition to the consideration of the materials of the bearing 50 and the bearing mount 52, control can be maintained on the lubricity of the contact surface between the spherical bearing 50 and bearing mount 52 by the addition of fluids or semi-solids to preclude the lens surface from moving out of engagement with the surface of the operation tool at the initial encounter to firstly allow prism to be removed. Removal of the prism takes place rapidly and the chuck stabilizes to provide full contact between the operation tool and the lens surface to continue the lapping operation with parallelism being maintained between the respective surface areas on the lens surfaces.

The chucks 36 and 38 of FIGS. 4 and 5 for convex and concave lenses, respectively, are similarly mounted. A ball pedestal 56 has end 58 threadably engaged with the chuck pedestal 32 with an opposite ball end 60 disposed within a lubricated compatible ball socket in a suitable bearing material 62. Both the ball end 60 and the material 62 may be of hardened steel. A snap ring 64 insures that the ball end 60 stays within the socket when the lens material is mounted and demounted from either chuck 36 or 38. From the illustrations it will be appreciated that because the ball end 60 is relatively small, it is able to be disposed particularly close to the lens surface being operated upon. This close relationship permits the center of curvature of the lens to be quite high and helps to stabilize the lens material when it is engaged with an operation tool.

It is easily appreciated that the chuck pedestal 32 in combination with the ball pedestal 56 can readily accommodate either chucks 36 or 38. Chuck 36, as is evident from the illustration of FIG. 4, provides in a three- The third part of the three-piece construction, bearing material 62, is as hereinbefore mentioned of any suitable material for providing readily pivotable action of the chuck 36 at the ball end 60 of the ball pedestal 56. Similarly to FIG. 4, a bell 72 of FIG. 5 has a recess 74 formed therein to carry a lens mounting pad 76 for cushioning the lens material during operation.

What is claimed is:

1. An optical lens generating machine for providing precision grinding techniques upon a lens material to obtain a lens having an optical axis, comprising:

an optical lens operation tool having an operating face for engagement with the lens material;

means for rotatably carrying said operation too] about a first axis of rotation;

a lens holder using only two bearings for carrying the lens material in relative free rotation, including; a lens holder head carrying the lens material, a radial bearing supporting the head for rotatable disposition of the lens material about a second axis of rotation with said radial bearing being the sole support for'said head, and a spherical bearing supporting the radial bearing for disposition of the second axis of rotation obliquely to the optical axis; and

means for supporting said lens holder at the spherical bearing relative to said operation tool.

2. The invention of claim 1, with the radial bearing being concentrically disposed about the second axis of rotation and having a first race fixedly engaging the spherical bearing, a second race fixedly engaging the lens holder head, and a plurality of ball bearings contained for revolving between the first and second races.

3. The invention of claim 1, with the spherical bearing being concentrically disposed about the second axis of rotation and being supported by a mount fixedly engaging said support means for providing a static friction force between the spherical bearing and mount to aid in coaxially aligning the second axis of rotation with the optical axis.

Patent No. 828 A83 Dated August 5,1974

Inventor(s) Raymond T. Blum and George J. Laughman It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 4, line 46, change "radical" to --radial--.

Signed; and sealed this 12th day of November 1974.

(SEAL) Attest:

McCOY M. GIBSON JR. C. MARSHALL DANN Attesting Officer Commissioner of Patents FORM PC4050 H0459) USCOMM-DC 60376-P69 0.5. GOVERNMENT PRINTING OFFICE I969 O-J6G-334 

1. An optical lens generating machine for providing precision grinding techniques upon a lens material to obtain a lens having an optical axis, comprising: an optical lens operation tool having an operating face for engagement with the lens material; means for rotatably carrying said operation tool about a first axis of rotation; a lens holder using only two bearings for carrying the lens material in relative free rotation, including; a lens holder head carrying the lens material, a radial bearing supporting the head for rotatable disposition of the lens material about a second axis of rotation with said radial bearing being the sole support for said head, and a spherical bearing supporting the radial bearing for disposition of the second axis of rotation obliquely to the optical axis; and means for supporting said lens holder at the spherical bearing relative to said operation tool.
 2. The invention of claim 1, with the radial bearing being concentrically disposed about the second axis of rotation and having a first race fixedly engaging the spherical bearing, a second race fixedly engaging the lens holder head, and a plurality of ball bearings contained for revolving between the first and second races.
 3. The invention of claim 1, with the spherical bearing being concentrically disposed about the second axis of rotation and being supported by a mount fixedly engaging said support means for providing a static friction force between the spherical bearing and mount to aid in coaxially aligning the second axis of rotation with the optical axis. 